Refrigerating Apparatus

ABSTRACT

A refrigerating apparatus ( 10 ) includes a refrigerant circuit ( 11 ) in which a compressor ( 20 ), a radiator ( 14 ), an expander ( 30 ), and a cooler ( 15 ) are connected to each other in order through refrigerant pipes, in which a rotating shaft ( 22 ) of a motor is connected to a compression mechanism ( 21 ) included in the compressor ( 20 ) while a rotating shaft ( 32 ) of a generator ( 33 ) is connected to an expansion mechanism ( 31 ) included in the expander ( 30 ). The refrigerating apparatus ( 10 ) further includes an electric power input mechanism ( 41, 43 ) for allowing the generator ( 33 ) to function as a motor. This secures the operation of the expander ( 30 ) at a start of the apparatus to secure the start of a system, thereby attaining reliable control of the start-up performance at the start.

TECHNICAL FIELD

The present invention relates to a refrigerating apparatus of a typeincluding an expander for motive power recovery as an expansionmechanism of a refrigeration cycle, which is connected to a generatorand is not mechanically connected to a compressor through a shaft.

BACKGROUND ART

There have been conventionally known refrigerating apparatusesperforming a refrigeration cycle by circulating refrigerant in arefrigerant circuit, which are widely used for the purpose of airconditioning and the like. For example, Patent Document 1 discloses arefrigerating apparatus including a compressor for compressingrefrigerant and an expander for motive power recovery for expanding therefrigerant. In a refrigerating apparatus shown in FIG. 1 in PatentDocument 1, the expander is connected to the compressor mechanicallythrough a single shaft so that the motive power obtained in the expanderis utilized for driving the compressor.

Referring to a refrigerating apparatus shown in FIG. 6 in PatentDocument 1, the compressor and the expander are not mechanicallyconnected to each other, and a motor and a generator are connected tothe compressor and the expander, respectively, so that the compressorand the expander are independent of each other. In this refrigeratingapparatus, the compressor is driven by the motor to compress therefrigerant while the generator is driven by the expander to generateelectric power.

Patent Document 1; Japanese Unexamined Patent Application Publication2000-241033 SUMMARY OF THE INVENTION Problems that the Invention is toSolve

In the case where the compressor and the expander are connected to eachother through the single shaft, the expander starts operating, at thesame time as a start of the apparatus, by the driving power of the motorconnected to the compressor. While on the other hand, in the case wherethe compressor and the expander are not connected to each other throughthe shaft, when the compressor is operated by the motor at a start ofthe apparatus, the starting torque for the expander may be short, thoughthe pressure difference is caused before and after the expander, to leadto failure in operation of the expander. In other words, a system inwhich the compressor and the expander are mechanically independent ofeach other cannot cause a normal start of the apparatus in some cases toinvolve a problem that the start-up performance at a start is controlledunreliably.

The present invention has been made in view of the foregoing and has itsobject of attaining reliable control of the start-up performance, in arefrigerating apparatus in which an expander is not mechanicallyconnected to a compressor through a shaft and is connected to agenerator, by securing a start of a system by securely operating theexpander at a start of the apparatus.

Means for Solving the Problems

A first aspect of the present invention premises a refrigeratingapparatus (10) including: a refrigerant circuit (11) in which acompressor (20), a radiator (14), an expander (30), and a cooler (15)are connected to each other in order through refrigerant pipes, in whicha rotating shaft (22) of a motor (23) is connected to a compressionmechanism (21), which the compressor (20) includes, while a rotatingshaft (32) of a generator (33) is connected to an expansion mechanism(31), which the expander (30) includes.

The refrigerating apparatus (10) further includes an electric powerinput mechanism (41, 43) for allowing the generator (33) to function asa motor (23).

In the first aspect, provision of the electric power input mechanism(41, 43) allows the generator (33) to function as the motor (23), forexample, at a start. When the generator (33) functions as the motor (23)at a start, the expander rotates by itself regardless of the pressuredifference before and behind the expander (30). Hence, the apparatusstarts normally.

Referring to a second aspect of the present invention, in the firstaspect, there is provided a control mechanism (45) for allowing theelectric power input mechanism (41, 43) for the generator (33) tooperate at a start of the expander (30).

In the second aspect, the control mechanism (45) is provided for usingthe generator (33) as the motor (23) at a start of the expander (30) toattain more secured operation of the expander (30) at the start. Afterthe start, the generator (33) generates the electric power by rotationof the expander (30) to recover the motive power.

Referring to a third aspect of the present invention, in the first orsecond aspect, the refrigerant circuit (11) uses carbon dioxide as arefrigerant.

The third aspect refers to the refrigerating apparatus (10) whichrecovers the motive power with the use of the expander (30) in therefrigerant circuit (11) using carbon dioxide as a refrigerant, whereinthe generator (33) connected to the expander (30) is used as the motor(23) at a start for start-up control and is used as the generator (33)in normal operation for motive power recovery.

EFFECTS OF THE INVENTION

According to the present invention, the electric power input mechanism(41, 43) allows the generator (33) to function as the motor (23). Forexample, when the generator (33) functions as the motor (23) at a start,the expander (30) rotates by itself regardless of the pressuredifference before and behind the expander (30) to cause the apparatus tostart normally, thereby attaining reliable control of the start-upperformance at the start.

In the second aspect of the present invention, the control mechanism(45) is provided for allowing the electric power input mechanism (41,43) for the generator (33) to operate at a start of the expander (30).This attains more secured operation of the expander (30) at a start.Hence, the start-up performance can be controlled more reliably at astart.

Referring to the third aspect of the present invention, in therefrigerating apparatus (10) which recovers the motive power by usingthe expander (30) in the refrigerant circuit (11) using carbon dioxideas a refrigerant, the start-up control can be performed by using thegenerator (33) connected to the expander (30) as the motor (23) at astart while the motive power can be recovered by using the generator(33) as the generator (33) in normal driving operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram of a refrigerating apparatus inaccordance with an embodiment of the present invention.

FIG. 2 is a block diagram showing electric control on a motor of acompressor and a generator of an expander.

INDEX OF REFERENCE NUMERALS

-   -   10 refrigerating apparatus    -   11 refrigerant circuit    -   14 radiator    -   15 cooler    -   20 compressor    -   21 compression mechanism    -   22 drive shaft (rotating shaft)    -   23 motor    -   30 expander    -   31 expansion mechanism    -   32 output shaft (rotating shaft)    -   33 generator    -   41 first converter (electric power input mechanism)    -   42 second converter    -   43 third converter (electric power input mechanism)    -   45 controller (control mechanism)

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below withreference to the accompanying drawings.

As shown in FIG. 1, a refrigerating apparatus (10) in accordance withthe present embodiment includes a refrigerant circuit (11). In therefrigerant circuit (11), a compressor (20), a radiator (14), anexpander (30), and a cooler (15) are connected to each other in orderthrough refrigerant pipes. Carbon dioxide (CO₂) as a refrigerant isfilled in the refrigerant circuit (11). The compressor (20) and theexpander (30) are provided at substantially the same level in height.

The compressor (20) is a hermetic compressor of generally-calledhigh-pressure dome type. The compressor (20) includes a compressorcasing (24) formed in a vertically cylindrical shape. Inside thecompressor casing (24), there are housed a compression mechanism (21), amotor (23), and a drive shaft (rotating shaft) (22). The compressionmechanism (21) is a generally-called rotary positive displacement fluidmachinery. Inside the compressor casing (24), the generator (23) isarranged above the compression mechanism (21). The drive shaft (22) isarranged so as to extend vertically to connect the compression mechanism(21) and the motor (23).

The compressor casing (24) is provided with a suction pipe (25) and adischarge pipe (26). The suction pipe (25) passes through the vicinityof the lower end of the body of the compressor casing (24) and has aterminal end directly connected to the compression mechanism (21). Thedischarge pipe (26) passes through the vicinity of the upper end of thecompressor casing (24) and has a start end open to a space above themotor (23) in the compressor casing (24). The compression mechanism (21)compresses the refrigerant sucked through the suction pipe (25) anddischarges it to the compressor casing (24).

In the bottom of the compressor casing (24), refrigerator oil as alubricant oil is reserved. Namely, an oil reservoir (27) is formed inthe compressor casing (24). The drive shaft (22) includes an oil supplymechanism for supplying the refrigerator oil from the oil reservoir (27)to the compression mechanism (21). Inside the drive shaft (22), an oilsupply path extending in the axial direction thereof is formed, thoughno shown. The oil supply path opens at the lower end of the drive shaft(22) and serves as a generally-called centrifugal pump. The lower endpart of the drive shaft (22) is dipped in the oil reservoir (27). Whenthe drive shaft (22) is rotated, the refrigerator oil is sucked from theoil reservoir (27) to the oil supply path by the operation of thecentrifugal pump. The refrigerator oil sucked in the oil supply path issupplied to the compression mechanism (21) to be utilized forlubrication of the compression mechanism (21).

The expander (30) includes an expander casing (34) formed in avertically cylindrical shape. Inside the expander casing (34), there arehoused an expansion mechanism (31), a generator (33), and an outputshaft (rotating shaft) (32). The expansion mechanism (31) is agenerally-called rotary positive displacement fluid machinery. Insidethe compressor casing (34), the generator (33) is arranged below theexpansion mechanism (31). The output shaft (32) is arranged so as toextend vertically to connect the expansion mechanism (31) and thegenerator (33).

The expander casing (34) is provided with an inflow pipe (35) and anoutflow pipe (36). The inflow pipe (35) and the outflow pipe (36) passthrough parts in the vicinity of the upper end of the body of theexpander casing (34). The inflow pipe (35) has a terminal end directlyconnected to the expansion mechanism (31). The outflow pipe (36) has astart end directly connected to the expansion mechanism (31). Theexpansion mechanism (31) expands the refrigerant flowing therein throughthe inflow pipe (35) and sends out the expanded refrigerant to theoutflow pipe (36). In other words, the refrigerant passing through theexpander (30) passes only through the expansion mechanism (31) withoutflowing into the internal space of the expander casing (34).

In the bottom of the expander casing (34), refrigerator oil as alubricant oil is reserved. Namely, an oil reservoir (37) is formed inthe expander casing (34).

The output shaft (32) includes an oil supply mechanism for supplying therefrigerator oil from the oil reservoir (37) to the expansion mechanism(31). Inside the output shaft (32), an oil supply path extending in theaxial direction thereof is formed, though no shown. The oil supply pathopens at the lower end of the output shaft (32) and serves as agenerally-called centrifugal pump. The lower end part of the outputshaft (32) is dipped in the oil reservoir (37). When the output shaft(32) is rotated, the refrigerator oil is sucked from the oil reservoir(37) to the oil supply path by the operation of the centrifugal pump.The refrigerator oil sucked in the oil supply path is supplied to theexpansion mechanism (31) to be utilized for lubrication of the expansionmechanism (31).

The construction of the refrigerant circuit (11) will be described next.One end of a first high-pressure pipe (P1) is connected to the dischargepipe (26) of the compressor (20) while the other end thereof isconnected to a pail of the expander casing (34) which is located abovethe generator (33). One end of a second high-pressure pipe (P2) isconnected to a part of the expander casing (34) which is located belowthe generator (33) while the other end thereof is connected to one endof the radiator (14).

To the other end of the radiator (14), one end of a third high-pressurepipe (P3) is connected, of which the other end is connected to theinflow pipe (35) of the expander (30). One end of a first low-pressurepipe (P4) is connected to the outflow pipe (36) of the expander (30)while the other end thereof is connected to one end of the cooler (15).The other end of the cooler (15) is connected to one end of a secondlow-pressure pipe (P5), of which the other end is connected to thesuction pipe (25) of the compressor (20).

The radiator (14) is an air heat exchanger (for example, an outdoor heatexchanger) for heat exchange between the refrigerant and first air flow(for example, outdoor air). The cooler (15) is an air heat exchanger(for example, an indoor heat exchanger) for heat exchange between therefrigerant and second air flow (for example, indoor air).

Between the compressor casing (24) and the expander casing (34), an oilequalizing pipe (38) is provided for connecting the oil reservoir (27)in the compressor casing (24) and the oil reservoir (37) in the expandercasing (34). The expander (30) is provided with an oil level sensor(39).

The refrigerating apparatus (10) includes a switchboard (40). Theswitchboard (40) is connected to an external alternating-current powersupply (50), the motor (23) of the compressor (20), and the generator(33) of the expander (30). The switchboard (40) has a function as anelectric power input mechanism (41, 43) for allowing the generator (33)to serve as a motor. The switchboard (40) includes a controller (controlmechanism) (45) for allowing the electric power input mechanism (41, 43)for the generator (33) to operate at a start of the compressor (20).

A structure of the switchboard (40) will be described with reference tothe block diagram of FIG. 2. The switchboard (40) includes a firstconverter (41), a second converter (42), and a third converter (43). Thefirst converter (41) has a function of an A-D converter (CON1) forconverting an alternating current to a direct current. The secondconverter (42) has a function of an inverter (INV1) for converting adirect current to a frequency-controlled alternating current. The thirdconverter (43) has both functions of an A-D converter (CON2) and aninverter (INV2).

The external alternating-current power supply (50) is connected so as tosupply an alternating current to the first converter (41). The firstconverter (41) is connected so as to supply a direct current to thesecond converter (42). The second converter (42) is connected so as tosupply a frequency-controlled alternating current to the motor (23) ofthe compressor (20). Whereby, the rotation speed of the motor (23) iscontrolled to adjust the operation capacity of the compression mechanism(20).

To the first converter (41), the third converter (43) is connected inparallel to the second converter (42). The third converter (43) iselectrically connected to the generator (33) of the expander (30). Innormal operation, the alternating current generated in the generator(33) is converted to a direct current through the A-D converter (CONT2)of the third converter (43) to be supplied to the second converter (42)together with the direct current from the first converter (41). Thedirect current from the third converter (43) is converted together withthe direct current from the external alternating-current power supply(50), which has been processed in the first converter (41), to analternating current in the inverter (INV1) of the second converter (42)and is then supplied to the motor (23) of the compressor (20).

At a start of the apparatus (10), the alternating current from theexternal alternating-current power supply (50) is supplied to the motor(23) of the compressor (20) and also to the generator (33) of theexpander (30). At that time point, the direct current converted by theA-D converter (CON1) of the first converter (41) is converted to thefrequency-controlled alternating current in both the inverter (INV1) ofthe second converter (42) and the inverter (INV2) of the third converter(43). Then, the thus converted alternating currents are supplied to themotor (23) of the compressor (20) and the generator (33) of the expander(30).

Wherein, a rotation speed command of the compressor (20) is input to thesecond converter (42) while a rotation speed command of the expander(30) is input to the third converter (43). On the basis of the thusinput commands, the frequencies of the alternating currents to besupplied to the motor (23) and the generator (33) are controlled.

—Driving Operation—

An operation of the refrigerating apparatus (10) will be described next.

During the operation of the refrigerating apparatus (10), a vaporcompression refrigeration cycle is performed by circulating therefrigerant in the refrigerant circuit (11). The refrigeration cycleperformed in the refrigerant circuit (11) is so set that the highpressure thereof is higher than the critical pressure of carbon dioxide,the refrigerant.

In the compressor (20), the motor (23) rotates and drives thecompression mechanism (21). The refrigerant sucked through the suctionpipe (25) is compressed in die compression mechanism (21) and is thendischarged to the compressor casing (24). The high-pressure refrigerantin the compressor casing (24) is discharged from the compressor (20)through the discharge pipe (26). The refrigerant discharged from thecompressor (20) fills the expansion casing (24) and is then sent to theradiator (14) to radiate heat to the first air flow (outdoor air). Thehigh-pressure refrigerant heat-radiated in the radiator (14) flows intothe expansion mechanism (31) of the expander (30).

In the expander (30), the high-pressure refrigerant flowing in theexpansion mechanism (31) through the inflow pipe (35) is expanded torotate and drive the generator (33). The electric power generated in thegenerator (33) is supplied to the motor (23) of the compressor (20). Therefrigerant expanded in the expansion mechanism (31) is sent out fromthe expander (30) through the outflow pipe (36). The refrigerant sentout from the expander (30) is sent to the cooler (15). In the cooler(15), the refrigerant flowing therein absorbs the heat from the secondair flow (indoor air) to be evaporated, thereby cooling the second airflow. The low-pressure refrigerant flowing out from the cooler (15)flows into the suction pipe (25) of the compressor (20).

During this normal operation, the alternating current from the externalalternating-current power supply (50) is frequency-converted through thefirst converter (41) and the second converter (42) to be supplied to themotor (23) of the compressor (20), and the alternating current generatedin the generator (33) of the expander (30) is frequency-convertedthrough the second converter (42) to be supplied to the motor (23) ofthe compressor (20). Accordingly, the amount of power to be suppliedfrom the external alternating-current power supply (50) can besuppressed.

—Operation at Start—

At a start, the controller (45) outputs a command for allowing thegenerator (33) connected to the expander (30) to function as the motor(23). Accordingly, the alternating current of the externalalternating-current power supply (50) is frequency-converted through thefirst converter (41) and the second converter (42) to be supplied to themotor (23) of the compressor (20) while being also frequency-convertedthrough the first converter (41) and the third converter (43) to besupplied also to the generator (33) of the expander (30) which serves asa motor at present.

Hence, the expander (30) can be started securely at the same time whenthe compressor (20) is started.

Effects of Embodiment

According to the present embodiment, the electric power input mechanism(41, 43) allows the generator (33) of the expander (30) to function as amotor. When the generator (33) functions as a motor at a start, theexpander (30) rotates by itself regardless of the pressure differencebefore and behind the expander (30) to start the apparatus (10)normally, thereby attaining reliable control of the start-up performanceat the start.

Other Embodiments

The above embodiment may have any of the following structure.

For example, the refrigerant is circulated in only one direction in therefrigerant circuit in the above embodiment but the present inventionmay be applied to a refrigerant circuit in which the refrigerantcirculating direction is reversible. The above embodiment presents abasic circuit configuration of the refrigerant circuit, which mayinclude various kinds of additional apparatuses in actual productdesign.

The above embodiments are merely essential examples and are thereforenot intended to limit the scopes of the present invention, applicableobjects, and uses.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful in a refrigeratingapparatus of a type including an expander for motive power recovery asan expansion mechanism of a refrigeration cycle, which is connected to agenerator and is not mechanically connected to a compressor through ashaft.

1. A refrigerating apparatus comprising: a refrigerant circuit (11) inwhich a compressor (20), a radiator (14), an expander (30), and a cooler(15) are connected to each other in order through refrigerant pipes, inwhich a rotating shaft (22) of a motor (23) is connected to acompression mechanism (21), which the compressor (20) includes, while arotating shaft (32) of a generator (33) is connected to an expansionmechanism (31), which the expander (30) includes, the refrigeratingapparatus further comprising: an electric power input mechanism (41, 43)for allowing the generator (33) to function as a motor (23).
 2. Therefrigerating apparatus of claim 1, further comprising: a controlmechanism (45) for allowing the electric power input mechanism (41, 43)for the generator (33) to operate at a start of the expander (30). 3.The refrigerating apparatus of claim 1, wherein the refrigerant circuit(11) uses carbon dioxide as a refrigerant.